The specific aim of this research proposal is to explore the role and mechanisms of inhibitors of gastric acid secretion at the level of the isolated parietal cell. The main thrust of the proposal will deal with exploring the stimuli responsible for enhanced prostaglandin synthesis in isolated parietal cells, and how this enhanced prostaglandin synthesis modulates the interaction between physiologic secretagogues in terms of gastric acid secretion as measured by cellular uptake of aminopyrine. Prostaglandin synthesis will be measured by two techniques. One will involve prelabelling the cells with 14C arachidonic acid and measuring the release of 14C prostaglandins and 14C arachidonic acid after the stimulation of the cells with carbachol, histamine and pentagastrin. The other will utilize the actual measuring of PGE2 in the incubation media using gas chromatography-mass spectroscopy after stimulation with the secretagogues. These studies will clarify the role of acid secretion per se in stimulating prostaglandin synthesis in parietal cells. The role of prostaglandin synthesis in modulating the interaction between carbachol and histamine, and pentagastrin and histamine, in terms of acid secretion will be examined by utilizing inhibitors of prostaglandin synthesis. The second part of my proposal will examine the role of adenosine receptors in modulating gastric acid secretion at the parietal cell. I have found in preliminary experiments that there are adenosine receptors at the R type on parietal cells that inhibit histamine stimulated acid secretion. I plan to explore the mechanism of this inhibition and further characterize the interaction between adenosine and secretagogues, especially as it relates to the generation of cAMP. In addition, utilizing specific inhibitors of adenosine receptors, inhibitors of adenosine reuptake, and adenosine deaminase, the physiologic importance of adenosine receptors will be assessed. The long-term objective of this proposal is to set up a scheme of how inhibitors of gastric acid secretion work at the cellular level. My hypothesis is that local hormones, like prostaglandins and adenosine, probably work at the parietal cell level directly, as feedback inhibitors affecting histamine stimulated adenylate cyclase.